Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 191855
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
255 PM EDT Wed Jul 19 2017

.SYNOPSIS...Weak high pressure will build into the region
through Thursday, followed by the potential for weak
disturbances Friday through Sunday. An upper level trough of
low pressure will move over the northeastern US to start the new
week.

&&

.NEAR TERM /THROUGH TONIGHT/...Convective coverage today has
been significantly less than yesterday. Experimental GOES-16
low-level water vapor imagery shows much drier air today than
yesterday which is greatly limiting deep convection to just
isold showers. Tranquil and very warm muggy tonight with lows in
the 70s in many areas and upper 70s in urban areas.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...As heights rise a
bit more and h85 temps rise into the low 20s (C), expect even
less convective coverage tomorrow than today. In addition, a
light w to nw sfc flow will develop lowering sfc dewpoints and
boosting temps in the mid to upper 90s hottest over western MD,
ern WV panhandle and wrn VA. Due to advection of lower
dewpoints, heat indices will likely fall below any heat advisory
criteria. Still hot nonetheless. Slight risk of some nocturnal
MCS activity to make it into western MD, but activity is likely
to dissipate as it crosses the Appalachians.

Hotter on Friday as h85 temps peak at 22C. A light sw flow over
Fredericksburg, southern MD and the urban areas will likely keep
sfc dewpoints higher with heat indices filtering around the 105
degree threshold. Temps west of the Blue Ridge could hit the
century mark with heat indices filtering with the new heat index
criteria there of 100F. Some convection can`t completely be
ruled out, but model guidance do not show good chances.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...

A front will stall across central Virginia Saturday. There is a
chance for showers and thunderstorms along this front. Highs will
once again reach the middle 90s in many areas.

The front will move north of the region as a warm front Saturday
night, keeping the chance for showers and thunderstorms present over
much of the region.

Upper level energy from the west will set up a trough of low
pressure on the leeside of the Appalachians Sunday into Sunday
night. Additional showers and thunderstorms could form along this
trough but could mainly be isolated to scattered. Highs will reach
the middle to upper 90s.

A cold front will approach the region Monday before pushing across
the region Monday night. Showers and thunderstorms will develop
along and ahead of this front. Some thunderstorms could be strong to
severe as wind shear increases some. Highs will reach the be in 90s
again, until the front ushers in cooler and drier air Monday night.

Broad high pressure will build in from the west and northwest
Tuesday through Wednesday. Temperatures will be nearly 10 degrees
cooler than previous days with a comfortable relative humidity with
respect to mid-Summer days and nights.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...VFR conditions
tonight through Fri with light and variable winds.

Mvfr to ifr conditions possible with showers and thunderstorms
Saturday through Sunday night. Ifr conditions would be mainly in
heavy thunderstorms. Winds southwest 5 knots Saturday. Winds light
and variable Saturday night. Winds southwest 5 to 10 knots Sunday,
becoming northwest around 5 knots Sunday night.

&&

.MARINE...Isolated t-storms possible today through Fri.

No marine hazards expected Saturday through Sunday night. Winds
southwest 5 to 10 knots Saturday and Saturday night. Winds southwest
10 knots Sunday and Sunday night.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...LFR
NEAR TERM...LFR
SHORT TERM...LFR
LONG TERM...KLW
AVIATION...LFR/KLW
MARINE...LFR/KLW



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